Good tips. I don't mind the complexity or cost. I'll look into the brain unit as sampler, if I have to run one through a laptop that would be fine too. I haven't used Ableton before, but hopefully it's easy enough to switch between projects so there wouldn't be a lag time between songs. That's a strong aspect of the Roland SPD-S, hit the big button to switch to next song = done.

I would still adore pads that were bar-like in design so as to take up less drum kit real estate, but I suppose circular pads with their two for one rims would mean I can get away with just 5 pads in total. I've got a tedious but fun new project I see.